Internal Medical Devices Powered Via Newly Developed Wireless Chips

Pacemakers and other implanted medical devices rely on bulky battery packs to power their essential functions and eliminating the need for these battery packs would revolutionize the medical device industry.

According to a new report published in the Proceedings of the National Academy of Sciences (PNAS), that revolution may be upon us as engineers at Stanford University have developed the novel system capable of wirelessly delivering power to chips planted deep within the body.

The project was led by Ada Poon, an assistant professor of electrical engineering at Stanford, who said the ability to wirelessly deliver power to internal devices could also revolutionize medicine and potentially eliminate the need for certain medications.

"We need to make these devices as small as possible to more easily implant them deep in the body and create new ways to treat illness and alleviate pain," Poon said.

The new study describes a pacemaker built by the Stanford team that is smaller than a grain of rice. The pacemaker can be powered or charged up again easily by positioning a power supply around the size of a credit card over the device, but outside the body.

A wireless power transfer then safely permeates into the body, using approximately the same energy as a cell phone. According to the study team, a separate laboratory that tests cell phones discovered that the system was well below the exposure amounts for human safety.

The new system relies on the use of electromagnetic waves and previous research categorized two distinct types of waves: far-field and near-field waves.

Far-field waves, used in radio broadcasts, can travel over long distances and when they hit biological tissue, they either bounce harmlessly off the body or get taken in by the skin as heat. Near-field waves have been safely utilized in wireless power systems, including those for devices like hearing implants. However, they can only transfer power over short distances, limiting their effectiveness deep inside the body.

The Stanford team was successfully able to combine the safety of near-field waves with the range of far-field waves by taking advantage of the fact that waves move differently when they hit various substances – such as air or internal tissues.

"With this method, we can safely transmit power to tiny implants in organs like the heart or brain, well beyond the range of current near-field systems," said study author John Ho, a graduate student in Poon's lab.

William Newsome, director of the Stanford Neurosciences Institute, said the system could lead to "electroceutical" treatments as replacements for drug therapies. He said these treatments might be more beneficial than drugs for some conditions because electroceutical methods would place devices near particular brain circuits to precisely regulate their activity – compared to drugs that often affect the entire brain.

"To make electroceuticals practical, devices must be miniaturized, and ways must be found to power them wirelessly, deep in the brain, many centimeters from the surface," said Newsome, a neurobiology professor who was not directly involved in the project. "The Poon lab has solved a significant piece of the puzzle for safely powering implantable microdevices, paving the way for new innovation in this field."